Some navigation systems use information that is received from a Global Positioning System (GPS) to display a moving object on a map. Such navigation systems may be used in, for example, ships, airplanes, and land vehicles, to determine location and velocity and/or to determine a traveled route. A navigation system may determine its latitude, longitude, altitude and the like from a radio signal that it receives from a plurality of satellites belonging to the GPS system, and may visually display the current location of the navigation system as a moving object on a map.
A navigation system in a land vehicle may display a map that shows roads with corresponding identifiers along with navigation information that may be used while driving, such as the vehicle's direction of travel, distance to a defined destination, current speed, a route traveled on the roads, and a route along the roads to the defined destination. Navigating with the displayed information may be difficult when, for example, roads are adjacent (i.e., geographically close) to each other, such as where a road splits and at road intersections. For example, a navigation system may incorrectly indicate that it is traveling on one road when it is actually traveling on another adjacent road. The navigation system may eventually correct its error by, for example, abruptly moving the displayed vehicle to the correct road. A driver may also have difficulty determining which of several adjacent roads should be taken, or has been taken, when the navigation system has insufficient certainty in its location, such as due to partial or complete blockage of the GPS signals, and/or when the level of detail that is displayed in the map (e.g., road names) is insufficient for such decisions.